|  | 4.5 | Layer 3 Design
| 4.5.2 |
How VLANs can create smaller broadcast domains
One important issue in a network is the total number of broadcasts, such as ARP requests. By using VLANs, you can limit broadcast traffic to within a VLAN and thus create smaller broadcast domains. VLANs can also be used to provide security by creating the VLAN groups according to function. As shown in Figure , a physical port association is used to implement VLAN assignment. Ports P0, P1, and P4 have been assigned to VLAN 1. VLAN 2 has ports P2, P3, and P5. Communication between VLAN 1 and VLAN 2 can occur only through the router. This limits the size of the broadcast domains and uses the router to determine whether VLAN 1 can talk to VLAN 2. This means you can create a security scheme based on VLAN assignment.